Sorting Objects Based on Custom Domain Class Methods

Question

I have a domain class, in which I've defined some methods which give the object a score based on different algorithms (eg. popularity).

I now want to retrieve a list of these objects sorted by one of these scores (eg. descending by popularity score).

Is there a way to do with with GORM?

Example class:

class SomeObject {
    String title

    Integer popularity() {
     //some algorithm
     return popularity
    }
}

Answer 1

There are three solutions I can think of. Assuming your dataset is small you can just return the entire list then sort it. For example

objectList.sort{popularity()}

Note based off the following link. http://jlorenzen.blogspot.com/2008/05/groovy-sort-list.html

If the calculation formula is simple you can always use a HQL query instead of the default find by methods. HQL is a query language similar to SQL that works on Hibernate objects which is what Gorm is built on. For more info see the following link. http://docs.jboss.org/hibernate/core/3.3/reference/en/html/queryhql.html If you don't need the calculated field to be updated in real-time and your calculations are to complex for HQL you can schedule a job to update the calculation results every hour or so, then store the generated result in a field of your domain class. For more information on Grails job scheduling see the following link. http://grails.org/Job+Scheduling+%28Quartz%29

Answer 2

Jared and you are right. Since it's a calculated value and not stored in the DB, GORM has no way of knowing anything about it. If you do as you say and create a new column for the value and then update it as needed you can use the SomeObject.list(order:'desc', sort: 'popularity', max:10) syntax.